Due to disease, trauma, or congenital malformation, the ossicles of the middle ear are sometimes damaged. The delicate joint between the incus and the stapes is termed the incudo-stapedial joint (ISJ). The ISJ is a cartilaginous joint having a tendency to ossify in older humans. When the joint is interrupted due to erosion of the joint or the incus itself, vibrations can no longer be transmitted from the incus to the stapes. The result is a conductive hearing loss related to the disrupted ossicular chain.
Medical implants have been developed to reconstruct the ossicular chain when a portion of the incus is missing. However, the entire incus had to be removed and replaced with a prosthesis. This approach destroys the natural joint between the incus and stapes and the lever function of the incus in relationship to the malleus and stapes.
One particular implant to address conditions when only the ISJ is eroded or ossified is shown in U.S. Pat. No. 5,306,299. This prosthesis is made from a hydroxylapatite. Particularly, the prosthesis comprises a block of hydroxylapatite having a cylindrical cavity intersecting with a U-shaped channel. The prosthesis is not adjustable. As such, the prosthesis must be provided in different sizes for different size ossicular chains. The prosthesis cannot be adjusted to conform to varying sized incus and stapes. Because of its mass and lack of features to stabilize its connection to the incus and stapes, it is possible for the prosthesis to migrate and extrude through the ear drum over a period of time. Concerns over the weight of the ceramic material and the overall mass of the prosthesis have been raised. Also, the hydroxylapatite material is inherently fragile, prone to breakage and cannot be easily modified to custom fit the incus or stapes head.
The present invention is directed to an adjustable, titanium ISJ prosthesis.